Networking as we know it is on the verge of a momentous change, thanks to a path-breaking technological concept known as software defined networking (SDN).
SDN represents a paradigm shift to the way networking elements operate. It is based on the OpenFlow Protocol and is the result of pioneering work by Stanford University and University of California, Berkeley.
Today’s networks and network elements have been largely closed and based on proprietary architectures and operating systems. Switching and routing of data packets happen in the same network elements, such as the router. SDN decouples the routing and switching of the data flows and moves the control of the flow to a separate network element namely, the flow controller. The motivation for this is that the flow of data packets through the network can be controlled in a programmatic manner.
A Flow Controller can be typically implemented in a standard PC. In some ways this is reminiscent of Intelligent Networks and Intelligent Network Protocol which delinked the service logic from the switching and moved it to a network element known as the service control point.
The OpenFlow Protocol has three components. The flow controller, the OpenFlow switch and the flow table, and a secure connection between the controller and switch. The protocol is an open source API specification for modifying the flow table that exists in all routers, Ethernet switches and hubs. The ability to securely control the flow of traffic programmatically opens up amazing possibilities.
Alternatively, existing branded routers can implement the OpenFlow Protocol as an added feature. The move will enable these routers and Ethernet switches to support production traffic and research based traffic using the same set of network resources.
The single greatest advantage of separating the control and data plane of network routers and Ethernet switches is the ability to modify and control different traffic flows through a set of network resources. In addition, SDNs also include the ability to virtualize the network resources. Virtualized network resources are known as a “network slice”, which can span several network elements including the backbone, routers and hosts.
Computing resources can be virtualized through the use of the Hypervisor which abstracts the hardware and enables several guest OSes to run in complete isolation. When an experimental FlowVisor network element is used in conjunction with the OpenFlow Controller, it is possible to virtualize the network resources.
Hence each traffic flow gets a combination of bandwidth, routers, traffic flows and computing resources.
Software Defined Networks (SDNs) are also known as Virtualized Programmable Networks owing to the ability for different traffic flows to co-exist in perfect isolation from one another, which allows for traffic flows through the resources to be controlled by programs in the Flow Controller.
The ability to manage different types of traffic flows across network resources opens up endless possibilities. SDNs have been successfully demonstrated in wireless handoffs between networks and in running multiple different flows through a common set of resources. SDNs in public and private clouds allow appropriate resources to be pooled during different times of the day based on the geographical location of the requests. Telcos could optimize the usage of their backbone network based on peak and lean traffic periods through the core network.
The OpenFlow Protocol has already gained widespread support in the industry and has resulted in the formation of the Open Networking Foundation (ONF). The members of ONF include behemoths Google, Facebook, Yahoo, and Deutsche Telekom, and networking giants Cisco, Juniper, and Brocade and IBM. Currently the ONF has around 43 member companies.
SDN is a tectonic shift in the way networks operate and truly represents the dawn of a new networking era.
Tinniam V Ganesh is a telecom expert with 25 years experience in the software industry. He blogs at http://gigadom.blogspot.com